In various flat-panel displays, organic light emitting displays (OLED) are expected to become the mainstream of next-generation flat-panel displays because of advantages such as a wide viewing angle, a desirable chromatic contrast effect, a high speed of response, and a low cost.
There are various types of OLEDs, for example, a top emission type, a bottom emission type or a double-sided emission type. To keep a needed storage capacitor, a sufficient area usually needs to be reserved. For a bottom emission type display and a double-sided emission type display, when a storage capacitor is disposed, an effective light emitting area (effective display area) becomes very small, resulting in a problem of a relatively small aperture ratio. In addition, to design an extra touch sensing element inside an OLED, a process becomes more complex, and a problem that an aperture ratio becomes smaller also occurs.